aoc2025/day5/main.go

package main

import (
	"fmt"
	"os"
	"sort"
	"strconv"
	"strings"
)

func main() {
	filename := "input0.txt"
	if len(os.Args) > 1 {
		filename = os.Args[1]
	}
	lines := readLines(filename)
	kitchen := parseKitchen(lines)
	fmt.Printf("%d\n", kitchen.countFreshIngredients())
	fmt.Printf("%d\n", kitchen.countEverythingFresh())
}

func readLines(filename string) []string {
	raw, err := os.ReadFile(filename)
	if err != nil {
		panic(err)
	}
	return strings.Split(string(raw), "\n")
}

type container struct {
	start uint64
	stop  uint64
}

func (i container) contains(id uint64) bool {
	return i.start <= id && i.stop >= id
}

type kitchen struct {
	coolers     []container
	ingredients []uint64
}

func (k kitchen) countFreshIngredients() uint64 {
	total := uint64(0)
INGREDIENTS:
	for _, ingredient := range k.ingredients {
		for _, cooler := range k.coolers {
			if cooler.contains(ingredient) {
				total++
				continue INGREDIENTS
			}
		}
	}
	return total
}

func parseKitchen(lines []string) kitchen {
	k := kitchen{
		coolers:     []container{},
		ingredients: []uint64{},
	}
	coolers := true
	for _, line := range lines {
		if line == "" {
			coolers = false
			continue
		}
		if coolers {
			parts := strings.Split(line, "-")
			cooler := container{}
			cooler.start, _ = strconv.ParseUint(parts[0], 10, 64)
			cooler.stop, _ = strconv.ParseUint(parts[1], 10, 64)
			k.coolers = append(k.coolers, cooler)
		} else {
			id, _ := strconv.ParseUint(line, 10, 64)
			k.ingredients = append(k.ingredients, id)
		}
	}
	return k
}

func (k kitchen) countEverythingFresh() uint64 {
	type pivot struct {
		id    uint64
		start bool
	}
	pivots := []pivot{}
	for _, cooler := range k.coolers {
		pivots = append(pivots,
			pivot{id: cooler.start, start: true},
			pivot{id: cooler.stop, start: false},
		)
	}
	sort.Slice(pivots, func(i, j int) bool {
		pi, pj := pivots[i], pivots[j]
		if pi.id < pj.id {
			return true
		}
		if pi.id > pj.id {
			return false
		}
		if !pi.start && pj.start {
			return false
		}
		return true
	})
	total := uint64(0)
	insideStarted := uint64(0)
	within := uint16(0)
	for _, pivot := range pivots {
		if pivot.start {
			if within == 0 {
				insideStarted = pivot.id
			}
			within++
		} else {
			within--
			if within == 0 {
				total += 1 + pivot.id - insideStarted
			}
		}
	}
	return total
}